Are you saying that there is already established production of oil and/ or gas on the parcel of land you are buying and that the current owner is currently receiving a flat $1,200 a year in royalty payments? If this is the case then this is the first time I have ever heard of a royalty being paid out this way. Usually it is stipulated in the lease what the royalty rate will be and is typically between 20-25% these days. That means they would get 20-25% of whatever their net mineral acre interest is in the producing Unit/ Well upon disposition and sale by the operator. Somebody who is leased at a 25% Royalty rate and owns 100% of the minerals under a given tract of land will receive much more $$ than somebody who leased at a 20% Royalty rate and only has a 25% mineral interest in the same tract. That being said, you do not have the information necessary to determine if $1,200 a year is “way too low compensation”. You would need to go to the county courthouse and run record mineral title from patent to determine what the seller of the parcel actually owns. You also state this is on a reserve so I am not sure how Colorado handles mineral interests on reserves.
To answer the first question: It is highly unlikely that the seller is including his mineral interest in the sale of the subject parcel. There will most likely be a mineral reservation in the deed you sign. Depending on the language in the deed, If there is no mineral reservation and seller owns the minerals, then you may be entitled to receive those payments as you would then be the new mineral owner. This almost never happens, especially when there are royalty payments being paid.
As far as your second question, I briefly touched on that above. One way to determine if somebody is a mineral owner is to do your own examination of courthouse property/ deed records. Most people choose to employ an attorney or a landman as most do not know where to begin when it comes to this approach. A simple method would be to go to the courthouse with the guys name and search it in their computer system if they have one. If not ask the county clerk for help running the name and pull all documents associated with his name. If you see that he has signed Oil and Gas Leases then chances are very good he is a mineral owner. Compare the legal descriptions on the lease/leases with the legal description of your parcel and if they match that is a pretty clear indication he/she owns at least a fraction of the minerals. Also sometimes you can google them as some websites have information on mineral owners and the area they own in. This method usually only captures folks who have current or past production of their minerals.
Sorry this is so long, hope it helps in some way!!